Hydraulic safety device for power presses and the like



June 2, 1931 H. PELS I 1,808,606

HYDRAULIC SAFETY DEVICE FOR POWER PREssEs AND THE LIKE Filed July 5, 1929 Patented June 2, 1931 UNETED STATES HENRY ZPELS," or BERLIN-GEARLOTTENBURG, GERMANY.

HYDRAULIC SAFETY DEVICE FOR- PO'WER PRE SSiES AND THE LIKE Application filed m 5, i929, Serial m5. 376,261, and in Germany September 4, i928. i

' This invention relates to a hydraulic safety device for :power presses and similar machines to compensate for excessive resistance 'oflered to the working stroke of theytool .5 carrier. The .safety device is. intended to protect the machine when the highest permissible pressure on the tool; carrier. is ex-v ceeded. Such safety devices hitherto have been provided with two valves, namely a sucfltion-Valve and a compression valve which, if the flow of the hydraulic medium is too great, owing to high speed ofthe piston, easily become damaged and leaky. V j

According to the present invention only one 15 valve is employed to control the flow of the hydraulic medium in both directions. The valve is opened when the maximum permissible pressure is exceeded and it remains wide open during the entire return period, so

90 that thehydraulic medium flows freely at low speed and only slight wear of the valve occurs.

The valve according to the invention is pressed onto its seat by a spring or by compressed air. I

which threepistons and threecylinders are required, wherebythe hydraulic medium is expelled from an intermediate cylinder by two: compression pistons, the diameter of which is many times that or the piston in the firstcylinder. V

In other knownarrangement's every time the hydraulic safety device has operated'the dium. All such arrangementsare very inconvenient. The present invention is constructionally much simpler, wear of, the

being shown in closed position."

Fig. 2 is a view similar toFig. l showing.

the valve in the open position. 1 i Figs. 3 and4: show a positively actuating mechanism-for thevalver x p cylinder must be refilled with hydraulicfmecan slide one onthe other.

Figs. to 8 showjthe cycle of operations of f the positively controlled valveif f Fig. 9 is a vertical section of a modified form of the apparatus whereinithe valve "is urged to closed position bycompressedairvjg On acarrier -1 the cutting, pressing or bending tools, not shown in the drawings, are secured: The carrier lis actuated by apressure ram 2 driven by a cam shaft (notshown) and has a-lower ball shaped part 3 mounted my;

in a piston 4 and held by a counter plate 5 a mounted on said piston. The piston 4 works in a cylinder 6'formed in the tool carrier 1.

A space 7 under the piston 4 is filled with fluid and communicates through channels 8 and'9 a6 l with an adjoining compartment 10and' a manometer 11 also carried by the tool carrier 1.

A valve 12 is arrangedon the side ofthe tool carrier 1 and thelower end l tiof the spindle 13 of said valveis movable toward andaway from one end of an intermediate channel 15 which connects the channels 8, and 9. The valvespindle 13; is acted upon by'a' spring 16 arranged in the valve casing the 1.5 l

pressure of which spring is adjustableby a cap 17 screwed onto-the valve casing. -'The adjustment depends up 'on'the maximumad-v missible pressure on the tool carrier 1.; The

valve spindle 13 passes on the one hand'eo throughthe-valve cap: 17 and on the other hand through the valve casingk fThe valve spindle 13 is screw threaded on its part which,

projects outside the cap 1 7, anda head 18 which is'screwed onsaid threaded part is .se- ".85 cured'in adjusted position bya counter nut A bracket20 is arranged on the carrier l Q and carriesa bolt 22. urgedby a spring 21- toward the'head .18. The bolt 22 is prevented .00 i from axial rotation by a guide 23; The end of the bolt 22 which is directed towards the valvejspindle hasa'fiat portion 24tflwhichengages under the head 18 when the spindle is raised. A notch 24L formed in the other end 'of the bolt 22 engages withva corresponding notch 25 in a bolt 26, secured to the pressure, ram 2; The 7 end faces of the two notches which face each other are inclined so that they The lifting of the valve spindle 13 is eflect- 7 ed by'the pressure of the fluid which passes stance the valve is opened if the maximum 7 pressure is not exceeded and consequentlyslf through the channels 8, and 9. r The lifting of the valve may however'be effected mechanically by the return movement of the pressure ram, as shown in Figs. 3 to 8'. In the latter inthe fluid has not flown overinto the adjoining chamber. This is intendedto prevent under all circumstances a'i'shortage ofzfluiduin .:the

cylinder chamber of the carrier.

- The valvespindle 13 (FigL39aiid L) -carries on its upper end a head'27 provided a bearing cavity engaged by a crankQS carried byone end of a shaft 30, mounted in bracket 29. A lever 31 is carriedby theotherend-of theshaft and has anf 'inclinedisurface 32 bearing'a-gainst a roller'38 mounted on a-holt QGsec'ured to-the pressure ram .Insteadof a spring. compressed air-may beused-topress the valve onto'its 'seatas shown in "Fig. 9.; It

is easy'to calculate :the pressurewhichhas'to be exerted on thevalve-in order't'o'obtainthe maximum pressure in the hydraulic pressure regulator. The pressure mayibe easily [adjusted on r a manometer 11 Fbllllh 1n the air conduit.

The'compresse'd air may 'further' be uti- 'lized to force back into the cyl1nder-7 the water, which has flown-outifrom the chamber "7 'below the piston into the adjoining chamber 10, and in this manner assist the suctionoperation of the'compression plston donuts-return stroke. This compressed air in {the .chamber10is'under a'pressure'of' ti to "10 at comp aredwitlr the excess pressure'in th'ej com- 145 jju'stinent of the pressure-which [the valve 1 1 to open the latter. QIt al o as- .sists the working of compression lpiston 4" during thesuction stroke. V Y

mospheres, whereas a pressure of about 350 maximum pressure is exceeded." 'Th'eslight air pressur'eiin'th e chamber 10-1s' -ins1'gn1'fic an't partm'ent below the coinpressio'n*piston.

The uselo'r"'compressed'air presentsman'y advantages. It 'faciIitatestlie -rmcurate admay act on Q'According to Fig. "9 a compression piston, 34'fixed0n the va.lv'eispindle.13;*works-in an Lair cylinder'35. The air cylinderis closed by a. screwedo'n cover through which the valve spindle 13'eX'tends with suitable pack in'gs. The air chamber above "the piston 34 permanently coimnunicateswith the air feed .nected to the discharge: chamber llo through conduit of an air compressor 1 through R an openingw, soflthat'the piston is always lun der-the pressure of the'compress'ed air. i The air conduit mm the compressor is "alsocon an orifice 3.7:s0' thatsaid chamber is 'alwa'ys r presssor.

filled 'I with compressed airfrom thelcomcommences its 7 upward movement, it carries ing chamber '10 through the .valve, whichis fhel'd openbyth'efb'olt22. Thevalve '13 is *thehead 18 of thevalve spindle 13ito permit .the same timeraised by the pressure {I a-m, fluid will :be drawn .in through .the' valveinto The operation is as follows:- I

If an undesirable resistance'y (Fig. 2) is.

offered by the material operated upon to the downward movement of the tool carrier 1 and the maximum working pressure for which "22 under thei'h'eadlS, after thepressure ram 2, has changed its position in relation to the tool holder 1. The fliiid then flows'from the cylinder 7 through the channels 8, '15 ,.9.into

.the adj oiningc'hamber 10. The pressure'ram 2 can thereforecontinue its stroke unimpeded without breakage occurring. 'After'the'pr'e'ssure ramfh'as attained its'lowestgposition and along "the piston 4 whereby; thejpressure :in thecylinder chamber 7 is reduced and'thelfluid is sucked into said chamber froni theadj'oinclosed only when the inclined face oifthe notch 25 on the bolt 26 Tests against-the inclined face of the notch 24a on the bolt 22 and the bolt-is thereby retracted to release the valve'to'be' movedto closed position v.un-

der the action of the spring '16. 'The machine is then ready for the neXt working stroke 1 I The head 18. is so adjusted longitudinally of the valve'spindle 13 that the bolt'22'enatmospheres'exist'sin the chamber? when 'the fgage'si'smd head only'when the missible' working pressure on the todl carrier 1 'and. on the pressure ra'm 2 is exceeded- 5 Accordingto Figs. 3 to 8, the pressureram 1.20m its downwardstroke movesto the right .(Figs. [5 .and 6); Thereby the-rollerf33 on" the bolt "26 moves away from; the inclined esu i faceuof the lever Consequently no 311110 movement istransmitted to the valve; ,Alfter the pressurer'am"has reached ifltsflowermost ingthe upward stroke oft-the ram 8-).

Qwingeto 'thiskmovement the shaft @30 is rocked and'the crankQSli-fts the valvespindle and.opens.the valve. As the piston f1 is-at the cylinder chamberofthev carrier. 'Assoon asgthe pressure riamxhas attained its uppermost position-the valve isag'ain closed. 1

positiontFig. 7 ),1 the roller 33 icomes again into contactwith theinclined surface ofthelever 31Qandpressesthe'leverrto one side dur- V 7 The surface32 may'beimadeofsucheshape that. the valve remains "-wide' open until the pres-sure'ram has completed its retiurn stroke. -f iByrthe means :ju stdescribedithevalvelcan Lo" 7 be caused to open asiiai asdesire d soithatslow flowing speeds of the fluid may be obtained and the wear of the valve reduced, the cer- .tainty existing that the cylinder chamber 7 of the carrier 1 is always sufliciently filled.

lVhen employing compressed air (Fig. 9) the valve is pressed onto its seat by an excess pressure above the air piston 34. On the return stroke of the piston 4 the water forced over into the discharge chamber 10 is forced back into the space 7 under the compression piston 4 on the one hand by the suction action of the piston 4L and on the other hand by the compressed air always present in the chamber 10.

I claim:

1. In a press comprising a reciprocating tool carrier and a ram for reciprocating said carrier, means for compensating for excessive resistance offered to the working stroke of said carrier, said means comprising a fluidcontaining cylinder formed in said carrier, a piston connected to the ram and working in said cylinder, a chamber carried by said carrier, a conduit connecting said cylinder and chamber, a valve normally closing saidconduit and opened by the pressure of the fluid in said cylinder and conduit when such pressure is caused by relative movement of said carrier and ram, during the working stroke of the ram, to exceed a predetermined de gree, and means operative during the return stroke of the ram to hold said valve in open position until the ram has completed its working stroke and operable to permit the valve to close as the ram approaches the end of its return stroke.

2. In a press comprising a reciprocating tool carrier and a ram for reciprocating said carrier, means for compensating for excessive resistance offered to the'working stroke of said carrier, said means comprising a fluidcontaining cylinder formed in said carrier, a piston connected to theram and working in said cylinder, a chamber carried by saidcarrier, a conduit connecting said cylinder and chamber, a valve normally closing said conduit and opened by the pressure of fluid in said cylinder and conduit when such pressure is causedby excessive resistance offered to the working stroke of the carrier to exceed a predetermined degree, and springactuated means to engage said valve when opened and holdit in open position and means operable at the end of the return stroke of the ram to disengage the last named means from said valve. 7 p

3. In a press comprising a reciprocating tool carrier and a ram for reciprocating said carrier, means for compensating for excessive resistance offered to the working stroke of said carrier, said means comprising a fluidcontaining cylinder formed in said carrier, a piston connected to the ram'and working in'said cylinder, a chamber carried by said carrier, a conduit connecting said cylinder and chamber, a valve normally closing said conduit and opened by the pressure'of the fluid in said cylinder and conduit when said pressure due to resistanceofferedto the work- ,ingstro'keof the carrierexceeds a predetermined degree, a spring pressed bolt engageable with said valve when in open posi- 7 tion to 'hold the v'alvein such position, and

means operative during the return stroke of the ram to'retract' said bolt; L y

4. In a press comprising a reciprocating tool carrier andaram for reciprocating said carrier, means for compensating for excessive resistance offered to the working stroke- 7 of said carrier, said means comprising a fluidcontainlng cyllnder formed in sald carr1er,-a

piston connected to the ram and working in I said cylinder, a chamber carried by said car- 'rier, a conduit connecting said cylinder and chamber, a valve normally closing said conduit and opened by the pressure of fluid in said cylinder and conduit when said pressure is caused by the resistance offered to the working stroke of said carrier to exceed a predetermined degree, said valve having'a stem of which the axis is substantially parallel to the'axis of saidpiston, a head longitudinally adjustable on said stem, means automatically engageable with said head when said valve is opened to hold the valve in open position, and means operable by said ram as the ram approaches the end 7 of its return stroke for disengaging said lastfluid-containingcylinder formed in said carrier, api'ston connected to the ram and workmg 1n said cylinder, a chamber carried by said carrier, a conduit connecting'said cylin der and chamber, a valve normally. closing a 'said conduit andhaving aheade'd stem, a.

rockshaft having at one end a crank ehgagingthe head of said'stem and at the other end having a lever provided with an inclined surface, and a roller carried by the ram and 'engageable with said inclined, surface during thereturn stroke of the ram to rock saidrock .shaft and'open said valve.

6. In a press comprising a reciprocating tool carrier and a ram for reciprocating said carrier, means for compensating'for exces sive resistance offered to the working stroke of said carrier, said means comprising a fluid containing cylinder formed in said ram, a piston working in said cylinder and connect ed to said ram, a closed chambercarried by said carrier, a conduit, connecting said cylinder and chamber, a closed cylinder carried by said carrier, a piston working in the latter cylinder, a valve carried by one side" of the last named piston to intersect and close said:

c'onduit, means efor admitting fluid gpressure xto said elosedcylinderfibove thepiston therei 'in for-urging said valve to closed position, means operative by said ram-during its return stroke to open said valve andmeans for admitting fluid pressure tosaid chamber as I said valve is opened to-expel the fluid therein v back through saidlconduit to said fluid-cont-aining cylinder ,When said valve is opened. In testimony whereof Ihave hereunto set my .hand.

. HENRY EELS. 

